PKOTOCOCCACEAE. 597 



5. DILOPHUS J. Ag. Till Alg. Syst. 2: 106. 1882. 



Segments mostly 0.3-1 mm. broad, the apices acute, acuminate or subobtuse ; medulla 

 2-4 cells thick or here and there only 1 cell thick. 1. D. guineensis. 



Segments mostly 1-2 mm. broad, the apices obtuse ; medulla 2-5 



cells thick at or near the margins, 1 or 2 cells thick in the middle. 2. D. alternans. 



1. Dilophus guineensis (Kiitz.) J. Ag. loc. cit. 108. 



Spatoglossum guineense Kiitz. Phyc. Gen. 339. 1843. 



? Dictyota Antiguae Kiitz. Tab. Phyc. 9 : 16. pi. 37. f. II. 1859. 



Dictyota guineensis 'Crouan ; Maze & Schramm, Alg. Guad. 126. 1870-1877. 



On rocks in shallow water in rather exposed situations. Rose Island, Berry 

 Islands, Great Bahama, Gun Cay, Watling's Island, Mariguana, Caicos Islands, Little 

 Inagua, and Great Ragged Island : Bermuda and Florida to Jamaica and Barbados. 

 Type from St. Thomas. 



Often proliferous along the middle line and often closely resembling Dictyota 

 cervicornis but usually darker on drying. 



2. Dilophus alternans J. Ag. loc. cit. 108. 



On rocks near low-water mark. Gun Cay, North Cat Cay, South Cat Cay, and 

 Caicos Islands : Florida to Barbados. Type from Key West, Florida. 



6. DICTYERPA Collins, Proc. Am, Acad. Arts and Sci. 37: 251. 1901. 



1. Dictyerpa jamaicensis Collins, loc. cit. 



On rocks in shallow water. South Cat Cay and Watling's Island : Jamaica. 

 Type from Jamaica. 



Resembles narrow conditions of DilopTius guineensis, but is more irregular in its 

 branching and is terete or subterete, with a medulla more than four cells wide. 

 Phyc. Bor.-Am. 780 in herb. N. Y. Bot. Gard. shows tetrasporangia (?) similar to 

 those of Dilophus guineensis. 



SUB-CLASS CHLOROPHYCEAE. 

 Family 1. PLEUROCOCCACEAE. 



1. PSEUDOTETRASPORA Wille, K. Norske Vidensk. Selsk. Skr. 



1906 3 : 20. 1906. 

 1. Pseudotetraspora Antillarum M. A. Howe, sp. nov. 



'Thallus subglobose, obovoid, pyriform, saccate, or allantoid, variously 

 wrinkled, constricted, or bullate, mostly 2-20 mm. in length or height, often 

 more or less explanate and lacunose with age, yellowish brown when living, 

 brownish or dark brown on drying ; cells subglobose or ellipsoid, mostly 3-7 /* 

 in maximum diameter. 



Enveloping leaves of Halodule and Thalassia and older parts of the thallus of 

 Chondria littoralis and other marine algae, in shallow water. Sometimes washed 

 ashore in great quantities. New Providence, Rose Island, Exuma Chain and Cat 

 Island. Type Howe 3^8 f Rose Island, Jan. 28, 1905. 



The species apparently differs from the Norwegian P. marina- Wille in its yel- 

 lowish brown color, its larger more saccate or allantoid thallus, and the somewhat 

 smaller cells. 



Family 2. PROTOCOCCACEAE. 



1. PROTOCOCCTJS Ag. Syst. Alg. 13. 1824. 



1. Protococcus viridis Ag. loc. cit. 



Pleurococcus vulgaris Naeg. Gatt. einzel. Alg. 65. pi. 4E. f. 2. 1849. 



On trunks of trees, etc. (det. F. S. Collins), probably common. New Provi- 

 dence : cosmopolitan. Type from Sweden. 



